Tinymail is a Webmail application designed for
mobile devices such as cellp hones and PDAs. It
requires the UW imapd server as a backend.
Features include content compression, message and
index pagination, and folder browsing. If you have
5000 messages in your inbox, tinymail lets you see
the most recent headers and read the first page of
a long email without incurring heavy connection
charges.

checkoutlook.pl is a Perl script to check mail on
Microsoft's Outlook Web-based mail reader. The
script currently only checks for new mail and then
logs out, printing the sender and subject of the
message, if applicable. The script can be run in
daemon mode, in which case it runs in silence
until a message is received.

Insight Server is a Linux-based email server
utilizing open source components to provide a
highly reliable, scalable, and cost effective
email solution for customers of all sizes. It's
designed to facilitate complete messaging and
collaboration capabilities within a company. It
supports all standard protocols, and provides
backup and recovery tools, server redundancy,
migration tools, and resource management.

libSmtpThread is a multi-threaded C++ library for
sending mail via SMTP. The library provides a
connection pool that initializes a set of threaded
SMTP connections. Emails can be pushed into the
pool, which accepts all mail and delivers them to
a free connection. The delivery to the SMTP server
is processed in a separate thread, so you don't
have to wait for mail to be accepted. It has been
successfully tested with Postfix.

Claros inTouch is an AJAX Web mail, instant messenger, address book, and note taker application. The main features are drag and drop support, background attachment uploading, built-in Bayesian spam protection that can identify junk mail on the fly, folder support for the POP3 protocol, compatibility with any POP3/IMAP and SMTP server, operating system independence, support for sending HTML email, and full MIME compatibility. It also features a unique AJAX instant messenger that is capable of talking with a Jabber server.

AlphaMail is a mod_perl webmail system with a C++ middleware component that is intended to make the system highly scalable. It supports many Unix variants with any RFC-compliant IMAP server (including UW, Cyrus, and Dovecot).

Inverse Lightning enhancer plugin enhances the
functionalities of the Lightning calendar plugin
for Thunderbird. It is meant to add better
integration with CalDAV compatible servers such as
SOGo. It provides support for CalDAV freebusy
information in the scheduling interface and in the
addressbook. It manages the iCalendar organizers
by taking into account the identities configured
in Thunderbird. And it fixes bugs found from time
to time in Lightning which are not yet fixed
upstream.

Instant OGo is a Linux-based groupware server
distribution. It contains all components required
to set up a mail and collaboration server from
scratch, including the Linux system software, the
Cyrus mail server, and the OpenGroupware.org
groupware server.